Device for cladding tubes by means of an explosive process

ABSTRACT

A device for internally cladding an outer tube with an inner tube by means of an explosion process. The device includes an outer tubular fixture (1) in which a workpiece in the form of the outer (2) and the inner (3) tubes can be placed; at least one end of the tubular fixture (1) is connected to an expansion chamber (7, 10); and a sealing cap (6) of easily destructed material is located between a respective expansion chamber (7, 10) and the workpiece. The sealing cap or caps (6) is/are intended to retain a liquid pressure-transmitting medium (5), preferably water, in the inner tube (3) prior to detonating an explosive substance (4) placed within the inner tube (3).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for cladding an outer tubeWith an inner tube made, for instance, corrosion-resistant material, inwhich the inner tube is bonded to the outer tube by means of anexplosion process.

2. Description of the Related Art

It is known to clad tubes, for instance steel tubes, for transportingoil and gas or other chemical products, with a thin internal tube madeof corrosion-resistant material, by means of an explosion process.

Hitherto, it has been necessary to carry out such tube claddingprocesses in separate firing places, mostly outdoors, due to noise andgases. This results in relatively high transportation and handlingcosts. Moreover, cladding processes are dependent on weather and windconditions.

The present invention relates to a device which enables tubes to be cladby explosion processes in a practically noiseless fashion and in aworkshop locality.

SUMMARY OF THE INENTION

The present invention thus relates to a device for cladding an outertube with an inner tube by means of an explosion process, and ischaracterized in that the device includes an outer tubular fixture inwhich a workpiece comprising said outer and said inner tube is intendedto be placed; in that at least one end of the tubular fixture isconnected to an expansion chamber; in that a sealing cap of easilydestroyed material is located between the expansion chamber and theworkpiece, said sealing cap or caps being intended to retain a liquidpressure transmitter, preferably water, in the inner tube prior todetonation of an explosive substance placed within the inner tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference toexemplifying embodiments thereof shown in the accompanying drawings, inwhich

FIG. 1 is a schematic axial sectional view of the inventive device;

FIG. 2 illustrates one end of the device in larger scale; and

FIG. 3 illustrates one end of an alternative embodiment of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates schematically a device constructed in accordance withthe invention. The device includes an outer tubular fixture 1 in which aworkpiece 2, 3 comprising an outer tube 2 and an inner tube 3 isinserted. The workpiece also includes one or more explosive charges 4,placed within the inner tube 3. At least one end of the tubular fixtureis connected to an expansion chamber 7, 10. The device also includessealing caps 6 which are made of an easily destroyed material and whichare intended to be fitted onto both ends of the workpiece and functionto retain a liquid pressure-transmitting medium 5, preferably water, inthe inner tube.

The caps 6 may be made of plastic, wood-fibre material or gypsum.

When detonating the explosive substance 4 located within the inner tube,the pressure transmitting medium will transmit a shockwave which causesthe inner tube 3 to expand towards the inner surface of the outer tube,said inner tube initially having a slightly smaller outer diameter thanthe inner diameter of the outer tube 2. Simultaneously the caps 6 willburst. The gas generated and the pressure transmitting medium therewithflow into the expansion chambers 7, 10.

About one cubic meter of gas at normal pressure per kilogram ofexplosive substance is generated by the detonation. If the tubularfixture were closed at its ends, the pressure generated by thedetonation would be extremely high, since the pressure-transmittingmedium is incompressible. Because the inventive device includesexpansion chambers and destructible caps, the pressure generated as thegases flow out into the expansion chambers will not be particularlyhigh. Naturally, the pressure that prevails after the detonation willdepend on the volume of the expansion chambers in relation to the amountof explosive used. Accordingly, the volume of the expansion chambers isconveniently chosen so that the pressure in the expansion vessels willbe relatively low after the detonation.

A valve 23, 24 may be provided in the wall of each chamber forevacuating the expansion chambers after detonation.

It is also conceivable to lower the pressure in the expansion chambersprior to detonation by evacuating air through the valves 23, 24.

Because the explosion takes place in a closed chamber consisting of thetubular fixture and the expansion chambers, no gas pressure wave will begenerated outside the closed chamber. This means that the level of noisegenerated will be very low in comparison with the noise generated whenusing known techniques. As before mentioned, the explosion bondingprocess can be effected indoors in a workshop locality. The presentinvention therefore enables an explosion bonding process to be effectedmore cheaply and more favourably than known techniques.

A method described in Swedish Patent Specification No. . . . (SwedishPatent Application No. 9200534-7) can be used advantageously with thepresent invention. That document describes a method of cladding an outertube with an inner tube, where the inner tube is made of acorrosion-resistant material, for instance. According to said document,a number of strings of explosive substance are placed at the innersurface of the inner tube, these strings being mutually spaced andextending from one end of the tube to the other. The inner tube isfilled with liquid, preferably water, which functions as apressure-transmitting medium, whereafter all explosive charges aredetonated simultaneously.

This results in a local metallurgical join or bond between the inner andthe outer tube adjacent the explosive charges. The detonation results inshockwaves which propagate in the pressure-transmitting liquid. Theshockwaves interfere with one another and generate high pressures withinthe inner tube 3, which therewith expands outwardly into abutment withthe outer tube 2. This results in a mechanical joint corresponding to apress joint between the inner and the outer tube over those regionswhere a metallurgical bond is not obtained.

FIG. 2 illustrates in larger scale the left part of the deviceillustrated in FIG. 1. The reference numeral 4 identifies a string ofexplosive substance which lies along the wall of the inner tube. Thereference numeral 11 identifies a ring of explosive substance whichextends along the wall of the inner tube. The reference numeral 12identifies a detonator which lies against the ring of explosive and issecured in the cap 6.

Instead of using strings of explosive which extend along the wall of theinner tube, an explosive charge may instead be placed axially andcentrally in the inner tube. In this case, however, no metallurgicalbond will be obtained, unless the charge is very powerful.

Furthermore, when using strings of explosive placed along the wall ofthe inner tube, a further axially and centrally placed explosive chargecan be used to enhance expansion of the inner tube.

As will be seen from FIG. 2, there is found initially a gap 9 betweenthe inner tube 3 and the outer tube 2. The outer tube 2 is centered inrelation to the tubular fixture 1 by means of a conical sleeve 17 whichcoacts with a conical bevel 18 in the inner wall of the tubular fixture1.

According to one preferred embodiment of the invention, the tubularfixture 1 has an inner diameter which exceeds the outer diameter 2 ofthe outer tube. The space 13 between the tubular fixture and the outertube is sealed against the surroundings. The tubular fixture 1 includesa throughlet 14 through which liquid, preferably water, can beintroduced into the space 13. By filling the space 13 with water or someother incompressible liquid, the workpiece can be easily inserted intothe tubular fixture 1 and removed therefrom after detonation.

FIG. 2 also illustrates throughlets 15, 16 for introducingpressure-transmitting medium to the inner tube 3.

Preferably, each end of the tubular fixture 1 is connected to anindividual expansion chamber, although the tubular fixture may beconnected to an expansion chamber only at one end thereof. In thislatter case, however, the workpiece is also preferably provided with asealing cap at each end of the outer tube. However, that end of theouter tube which lies against the closed end of the tubular fixture maybe sealed against said end.

FIGS. 1 and 2 show a flange connection between the tubular fixture andrespective expansion chambers. The flanges can be fastened to oneanother with bolts or by means of U-shaped clamps which project radiallyin over the flanges 19, 20; 21, 22. The flanges are sealed against oneanother by means of a seal 16.

The tubular fixture 1 can be given a significant length, for instance alength of 10 to 15 metres.

According to one preferred embodiment, the expansion chambers aremovable in relation to the tubular fixture, so as to provide easy accessto the interior of the tubular fixture and to the interior of theexpansion chambers. This can be achieved by mounting the expansionchambers 7, 10 on wheels 25, 26 which run on a rail 27 or some othersupportive surface. The tubular fixture 1, on the other hand, ispreferably fixed to the supporting surface with the aid of braces orstays 28, 29. Preferably, the expansion chambers 7, 10 are alsopivotally mounted in addition to being axially movable in relation tothe tubular fixture, so as to facilitate insertion and removal of theworkpieces and also to facilitate cleaning of the tubular fixture andthe expansion chambers.

According to one alternative embodiment, the expansion chamber orchambers is/are fixedly mounted to the tubular fixture and provided witha flap 30 at the end wall thereof, for insertion and removal of thework-piece. FIG. 3 illustrates the right-hand expansion chamber 10 ofthis embodiment. As indicated by the arrow 31, the flap is hinged.Although not shown, the flap is, of course, provided with locking meanswhich holds the flap closed during the process of detonation.

It will be evident from the foregoing that the present invention solvesthe problems associated with the known technique mentioned in theintroduction.

It is assumed in the aforegoing that the tubes concerned are straighttubes. However, the tubular fixture 1 may be curved so as to enablecurved tubes having the same or essentially the same radius of curvatureas the tubular fixture to be produced.

Since the aforesaid space 13 contains liquid, the tubular fixture 1 mayhave a much larger diameter than the outer tube 2. This enables theshape of the tubular fixture 1 to deviate from the shape of the outertube 2. The cross-sectional shape of the tubular fixture 1 may alsodeviate from a circular shape. For instance, the tubular fixture mayhave a square or rectangular cross-sectional shape.

Although the invention has been described with reference to differentembodiments thereof, it will be understood that the inventive device maybe modified in many ways with regard to its structural configuration.

The present invention shall not therefore be considered restricted tothe aforedescribed and illustrated embodiments, since modifications canbe made within the scope of the following Claims.

What is claimed is:
 1. A device for internally cladding an outer tubewith an inner tube by means of an explosion process, said devicecomprising: an outer tubular fixture in which a workpiece in the form ofthe outer tube and the inner tube is inserted; a closed expansionchamber connected with at least one end of the tubular fixture; a firstsealing cap of easily destroyed material is located between theexpansion chamber and the workpiece and a second sealing cap is locatedat an opposite end of the tubular fixture, said sealing caps provided toretain a liquid pressure-transmitting medium in the inner tube prior todetonating an explosive substance within the inner tube (3).
 2. A deviceaccording to claim 1, wherein a second closed expansion chamber isconnected with the opposite end of the tubular fixture, and the secondsealing cap is located between the second expansion chamber and theworkpiece and in made from easily destroyed material.
 3. A deviceaccording to claim 1, wherein the expansion chamber connected with thetubular fixture and is displaceable relative thereto, to provide easyaccess to the interior of the tubular fixture and to the interior of theexpansion chamber.
 4. A device according to claim 1, wherein theexpansion chamber is fixedly mounted to an end of the tubular fixtureand includes a movable flap at an end spaced from the tubular fixture topermit insertion and removal of the workpiece through the expansionchamber.
 5. A device according to claim 1, wherein the tubular fixturehas an inner diameter which is larger than the outer diameter of theouter tube to define a space therebetween; wherein the space between thetubular fixture and the outer tube is sealed; and wherein the deviceincludes a throughlet through the tubular fixture through which a liquidis introduced into said space.